This invention relates to an intravascular catheter which exhibits improved resistance to kinking in the tip even when the tip is thin-walled and flexible.
Intravascular, and particularly intravascular catheters for angioplasty or angiography are equipped with a pliable tip to facilitate the advancement of the catheter through the vascular system of a patient toward its objective, typically a coronary artery or a chamber of the heart. The proximal majority of the catheter length is typically flexible but firm, being generally equipped with a tubular, braided or otherwise crossing wire reinforcement member to provide torsional stiffness and pushability to the catheter. Thus the catheter may be reliably rotated from the proximal end to cause the distal end to rotate a substantially equal amount.
However, the distal tip end of the catheter is desirably more flexible than is generally possible with such a tubular braid-reinforced catheter section. Accordingly, in the prior art most catheters of this type carry no wire reinforcement at all at the distal tip.
Because of this, a problem arises in that, while the distal tip portions of prior art catheters are adequately flexible and soft so that advancement of the catheter does not injure vascular or heart tissues, the tip portion is subject to collapsing or kinking when it is directed around a bend in a branched blood vessel or the like. This of course is deemed undesirable, even if the plastic material of the tip portion is capable of springing back into uncollapsed condition when it is straightened out again.
Accordingly, there is a need for a catheter which has a high torsion resistance in its proximal section in accordance with the prior art, but which exhibits a highly flexible tip which, nevertheless, has substantial collapse resistance, particularly resistance against kinking as the tip is directed about a bend in a blood vessel.
In accordance with this invention, a catheter is provided which has a distal portion which may be soft and pliable as needed, but in which the distal portion is strongly resistant to collapse so that it may be directed through a labyrinth of branching blood vessels or the like without damaging tissues, but without collapsing or kinking. The resulting catheter exhibits improved characteristics over prior art catheters, particularly for the well-known PTCA procedure or any other angioplasty or angiography procedure.
As a further advantage, the plastic material out of which the distal portion of the catheter of this invention can be made may be inherently softer than in the prior art, for added tolerability of catheter advancement through tissues. At the same time, the distal section exhibits its improved and desired resistance to collapse or kinking.